Abstract

Spontaneous breathing trial (SBT), a routine procedure during ventilator weaning, entails cardiopulmonary stress for the ventilated patient, which is higher in the patients failing the trial. IL-18, a pro-inflammatory cytokine playing a role in the host defence against infectious diseases and tumour growth, is induced by catecholamines or angiotensin, mediators overexpressed during weaning. Aim of this study was to explore the effect of weaning on IL-18 levels locally in the airways, and systemically.

26 mechanically ventilated patients, who underwent a 30 minute SBT, were classified as SBT failure or success. Bronchial aspirates and blood samples were drawn before, 30 mins, and 24 hours after the SBT.

IL-18 levels in bronchial aspirates increased from mechanical ventilation to spontaneous breathing in the SBT success group at the end of 30 minutes (68.5 pg/ml (11-823) vs 78.5 pg/ml (29-723), p&gt;0.05, values are expressed as median (range)), and 24 hours later (101 pg/ml (34-903), p&gt;0.05). On the contrary, in the SBT failure group, IL-18 levels decreased at the end of 30 min SBT (85 pg/ml (39-155) vs 50.4 (8-148.5), p=0.06), and remained decreased 24 hours later (42 pg/ml (3.5-385, p=0.07), correlating with bronchial lymphocyte counts (r=0.762, p=0.028). The systemic levels of IL-18 were significantly higher compared to local levels (p&lt;0.05), and in the SBT failure group compared to SBT success group at all time points, with no significant variation between measurements per group. Our data suggest that SBT stress during ventilator weaning induces the production of IL-18 locally and systemically probably via different pathogenetic pathways.